#include<iostream>
using namespace std;
int main()
{
	int n, x;
	cout << "input n and x:" << endl;
	cin >> n >> x;
	double p(int, int);
	cout << p(n, x) << endl;

	return 0;
}
double p(int n, int x)
{
	if (n == 0)
		return (1);
	else if (n == 1)
		return (x);
	else
		return ( ((2 * n - 1) * x * p(n - 1, x) - (n - 1) * p(n - 2, x)) / n);

}